many differ on this subject, if racing your birds, i would say keep clean as much as poss, [bone dry droppings are "clean" but damp droppings lying over 24 hours,, a haven for desease] personally i like to scrape the perches /boxes/floor each day, ,,in winter have easybed under the perches , but still scraping the loft out each day, and taking the worst of the muck from the easybed,,[on dry days lightly spray the loft with virkon s,,, my thoughts are not only to keep the loft clean, but to bond with the birds, hopefully producing less stress by having tame birds, that know me well, only my opinion